The file being referred to is located here:
--C:\Documents and Settings\<Your User Name>\Application Data\Adobe\Dreamweaver CS4\en_US\Configuration\Shared\Webassist\Surveyor\Library
This error may have to do with your operating system. One thing you can try is to shut down Dreamweaver and extension manager and delete the WinFileCache#####.dat file located here:
--C:\Documents and Settings\<Your User Name>\Application Data\Adobe\Dreamweaver CS4\en_US\Configuration\